Acharei begins with a lengthy description of the special Yom Kippur service to be performed in the Mishkan by the Kohen Gadol. The service included the lottery selection from among two identical goats, one of which would become a national sin offering and the other to be pushed off a cliff in the desert as the bearer of the people’s sins (the ‘scapegoat’). We also find described the command that Yom Kippur and its laws of fasting and refraining from work be observed eternally by the Jewish people as a day of atonement. Acharei concludes with a listing of the immoral and forbidden sexual relationships, and the command that the Jewish people maintain and ensure the holiness of the land of Israel.
Kedoshim begins with G-d’s command to the entire nation of Israel to be holy, emulating the supreme sanctity of G-d Himself. The Torah goes on to delineate a multitude of mitzvos through which we can achieve sanctity, covering a wide variety of subjects, both positive commandments and negative injunctions, dealing with our unique relationships to G-d and our fellow man.
Amongst the highlights; revere your parents, guard Shabbos from desecration, have honest dealings with our neighbors, refrain from tale-bearing, don’t hate your brother in your heart, and the well-known commandment to love your friend as yourself. Kedoshim concludes with the commandment that we be a holy and distinct people from among the nations of the world.